This invention relates to improvements in a vacuum circuit interrupter.
A conventional vacuum circuit interrupter has comprised an evacuated envelope, and a pair of electrode assemblies, one stationary and one movable, and disposed in opposed relationship within the evacuated envelope, the stationary assembly having a stationary electrode rod extending through and sealed in one end of the envelope and the movable assembly having a movable electrode rod movably extending in hermetic sealed relationship through the other end of the envelope.
The movable electrode assembly has comprised a metallic coil electrode including an annular holder fixedly fitted onto the extremity of the movable electrode rod, four radial arms extending from the holder radially and at equal angular intervals of 90 degrees perpendicularly to the axis of the annular holder and having equal lengths, four circumferential arms from the extremities of the radial arms running in a common direction along a common circle concentric with the annular holder and terminating short of the adjacent radial arms to form four coil sections in the form of circular arcs equal in arc length to one another, and four short connections extending from the extremities of the circumferential arms perpendicularly thereto and spaced from the mating electrode rod and with flat ends flush with one another. A main electrode in the form of a metallic disc has been disposed on the four flat ends of the connections to complete the movable electrode assembly. The stationary electrode assembly has been identical in structure to the movable electrode assembly as described above.
Upon the occurrence of an electric arc at the center of the main electrode, a current has flowed through current paths each traced from the center of the main electrode through the associated connection, the mating circumferential arm and the mating radial arm of the coil electrode and thence to the associated electrode rod through the annular holder so as to establish an axial magnetic field on the surfaces of the main electrodes and in the space therebetween to effectively interrupt the particular overcurrent.
In conventional vacuum circuit interrupters such as described above, the distance between the coil electrode and the surface of the main electrode or the space between the opposed main electrodes is rather large so that magnetic flux leaks from the axial magnetic field established by the coil electrode. As a result, a uniform magnetic field has been unable to be established on the surfaces of the main electrodes and in the space therebetween. Also in order to establish the magnetic field, it has been required to use a coil electrode in the form of circular arcs about the associated electrode rod and also radially. This has resulted in the disadvantages that the structure is complicated and lacks in mechanical strength and a compact structure is impossible.
Accordingly it is an object of the present invention to provide a new and improved vacuum circuit interrupter capable of establishing a uniform, stable axial magnetic field on the surfaces of the particular electrodes serving as contacts and more particularly on the peripheral portions of the surfaces of the electrodes and in a space formed therebetween with a simple structure and without the necessity of using a coil electrode such as that previously required.